1. Field of the Invention
The present invention relates generally to rack mount computer systems. More specifically, power distribution systems and methods for adaptation of the power distribution to computer systems to varying electrical loads and/or varying power supply inputs are disclosed.
2. Description of Related Art
Many of today's more complex computing systems such as computer server systems are often rack-mounted systems in which a number of removable electronics modules, such as electronics trays, are positioned and stacked relative to each other in a shelf-like manner within a frame or rack. Rack-mounted systems allow the arrangement of several of the electronics modules in a vertical orientation for efficient use of space. Each electronics module can be slid into and out of the rack-mounting system. Typically, the electronics modules are inserted from the front of the rack and various cables such as data cables, power cables, etc., are connected to the electronics modules at the front and/or rear of the rack.
Each electronics module may correspond to a different server or each electronics module may hold one or more components of a server. Examples of electronics modules include modules for processing, storage such as random access memory (RAM), network interfaces and controllers, disk drives such as floppy disk drives, hard drives, compact disk (CD) drives, and digital video disk (DVD) drives, parallel and serial ports, small computer systems interface (SCSI) bus controllers, video controllers, power supplies, and so forth. A server farm in today's computing environment may include numerous racks that hold various types of computer-related modules.
Rack mount computer systems are often shipped to and used in locations such as central offices in different countries with varying electrical systems serving as the power inputs to the rack systems. Typically, each server uses a universal input power supply module which is a power supply that allows the server to operate properly with input voltages from 90V-240 VAC (volts alternating current). For example, in North America, the electrical systems typically provide 115V/15 A (volts/amperes), 115V/20 A and/or 208V/20 A circuits while 230V/16 A and/or 230V/32 A circuits are common in Europe.
With different voltages and amperages at various locations, the rack mount computer systems need to be wired accordingly in order to distribute power efficiently and to maintain load balancing to prevent circuit overload. Currently, the rack mount computer systems may be shipped ready to be adapted and configured by a service technician to the electrical system available at the destination location. However, such a process is time consuming, labor intensive and costly, particularly as a large rack typically have dozens of electrical plugs that need to be wired to a corresponding electrical outlet or source. With multiple racks, such a process may take several days for a service technician to configure just the wiring for the numerous racks being installed at the destination location.
In addition, at many collocations, service providers often have to pay for each circuit used. Thus, it would be desirable to design the computer systems such that the systems draw the maximum amount of power from each outlet or circuit being used. However, over time, the computer systems are likely to be updated and/or upgraded, for example, with faster central processing unites (CPUs), more memory, larger disk drives, etc. Such upgrades typically increase the amount of power drawn by the system. To account for the increased power requirements of possible future upgrades, the engineering designing the rack system may estimate the amount of power requirement increases and include and account for this estimate in the power circuit configurations. However, if the estimate turns out to be too low, there is a large cost associated with rewiring the racks for the necessary extra service cords. Even if the estimate turned out to be sufficient, a given rack may spend most of its life operating at well below its maximum power rating. Such under-utilization of the available power is not cost effective given that the service provider pays for each circuit used.
Furthermore, even if no upgrades are performed, during an initial installation testing, the systems are typically operated at substantially more current than that drawn during normal use. While the testing is performed only for a short period of time (e.g., a few days) relative to the useful life of the system (e.g., three years), the system nonetheless needs to be provisioned with sufficient current to meet this unusually high demand during the testing. The test may be performed by wiring the system to additional power cords and then rewiring the system to use fewer power cords at the lower currents of normal operation, a time consuming task. The alternative may be to unplug half of the servers and test each half of the rack sequentially, thereby doubling the test time.
Thus, it would be desirable to provide a system and method to conveniently adapt the distribution of power for a computer system to varying electrical loads and/or with varying power inputs.